Control of Gene Expression in Bacteria

Control of Gene Expression in Bacteria - Chapter 17 Gene...

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Unformatted text preview: Chapter 17: Gene Expression in Bacteria I. Gene Regulation and Information Flow a. Mechanisms of Regulation i. A cell could avoid making the mRNAs for particular enzymes if there is no mRNA, then ribosomes cannot make the gene product. Transcriptional control occurs when regulatory proteins affect RNA polymerase’s ability to bind to a promoter and initiation transcription. Transcriptional control is particularly important due to its efficiency – it saves the most energy for the cell, because it stops the process at the earliest possible point. ii. If the mRNA for an enzyme has been transcribed, the cell might have a way to prevent the mRNA from being translated into protein. Translational control occurs when regulatory molecules alter the length of time an mRNA survives before it is degraded by ribonucleases, or affect translation initiation, or affect elongation factors and other proteins during the translation process. Translational control is advantageous because it allows a cell to make rapid changes in the relative amounts of different proteins. iii. Some proteins are manufactured in an inactive form and have to be activated by a chemical modification, such as the addition of a phosphate group. This type of regulation is post-translational control. Post translational control provides the most rapid response of all three. b. Metabolizing Lactose – A Model System i. To use lactose E. coli must first transport sugar into the cell. Once lactose is inside the enzyme -gal catalyzes a reaction that breaks the sugar down into...
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This note was uploaded on 03/16/2011 for the course BIO 180 taught by Professor Chamberlain during the Spring '08 term at Staten Island.

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Control of Gene Expression in Bacteria - Chapter 17 Gene...

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